The investigators have developed a large animal model of cardiac allograft vasculopathy using partially inbred miniature swine, which differ from rodents in their immune responses, cardiovascular physiology and susceptibility to atherosclerosis. Preliminary data demonstrate that coronary lesions develop in hearts transplanted across a class I or full MHC barrier, but not in hearts transplanted across a class II MHC barrier or in hearts matched at the entire MHC. Furthermore, vasculopathy is prevented when recipients are rendered tolerant to the donor class I alloantigens. Based on these findings, the investigator proposes five specific aims: 1) Determine the immunogenetic requirements for the development of cardiac allograft vasculopathy in miniature swine; 2) Determine the pathways of cellular immunity which induce coronary lesions in MHC class I disparate but not class I disparate hearts by extracting and analyzing graft infiltrating cells; 3) Determine whether humoral antibodies contribute to vasculopathy in class I mismatched cardiac grafts using flow cytometry, cytotoxicity assays, and antibody transfer techniques; 4) Assess the role of selected cytokines and adhesion molecules in the induction of cardiac allograft vasculopathy using Northern blot analysis; 5) Evaluate the efficacy of anti CD8 monoclonal antibody in preventing or reversing vasculopathy in transplanted hearts using the pig monoclonal antibody 76 2 11.